Measures of differences in postural steadiness for healthy neurotypical young adults when vision is removed

Abstract

Stable balance is a prerequisite for basic mobility and impaired balance is a known factor in unintended falls. Balance is controlled by proprioception, visual and vestibular systems. Previous research using a force plate has mainly focused on balance for a stable two-foot stance, when vision was removed (i.e., eyes closed). Less research exists for more challenging stances on a force plate with and without vision. The goal of this study is to characterize the balance of neurotypical (NT) young adults in six different stances: two-feet stance (2F), feet tandem (TD) (heel to toe on a line) and standing on one foot (1F); all performed with eyes open (EO) and eyes closed (EC). This goal was accomplished by measuring the center of pressure (COP) on a force plate to determine if statistically significant differences exist between the six stances as measured by specific postural parameters. Thirty-five (19 females, 16 males; age = 23.7 ± 02.8 years) NT young adults stood as still as possible on an ATMI force plate in one of six stances for 30 seconds. The data collection order was randomized by the six stances and repeated in four blocks of testing (A, B, C, and D), giving a total of 24 trials for each participant. The order of testing in block B was reversed from block A; blocks C and D were a repeat of blocks A and B, respectively. Loss of stance was visually identified and the start and stop times were recorded. Data collected from the time they lost stance and regained it were removed and not used in calculations. Force plate data was summarized to the following postural parameters: average distance from the mean COP (mean absolute deviation) in the anterior posterior (MdistAP, mm) and medial lateral (MdistML, mm) directions; mean velocity of the center of pressure (MVelocity, mm/sec); and total path length of COP (Totalpathlength, mm) using the equations provided by Prieto. An Anderson-Darling test for normality was performed on the data grouped by stance and gender for all parameters. Kolomogorov-Smirov test was used to determine if differences existed between stances when compared to two feet eyes open (2FEO). The literature states that smaller values of these parameters imply better balance. Results are found in the following table and indicate that parameter magnitude changes with stance and vision. For this population, 2FEO and 2FEC are the least challenging postures increasing in difficulty for TEO and 1FEO, TEC, and IFEC, respectively; and loss of vision played a role in the difficulty of the stance. This data can be used to develop a database for healthy young adults to compare adults in different age groups and health conditions in identifying deficits in patient balance capability.